Dendritic cells (DC) are strategically located at the environmental interface, serving as immunological sentinel and tissue-resident antigen presenting cells. Upon exposure to infectious microorganisms or "danger signals", DC produce pro-inflammatory mediators, undergo maturation, and migrate to lymph nodes to activate naive T cells. Thus, DC activation is the initial and key event linking innate to adaptive immunity. We will employ the DC-based biosensor system to study DC activation processes systematically and to develop novel DC-stimulating agents. Specific aims are: 1) To optimize the DC-based biosensor. We have developed a DC biosensor prototype by transfecting XS106 DC line with 13 luciferase reporters with different cis-enhancers and identified various microbial, biological, pharmacological, and physical agents that activate distinct transcription regulatory pathways in DC. We will optimize this system by isolating DC clones permanently expressing EGFP reporter constructs. 2) System validation. We will test the utility of the DC biosensor by testing currently known DC-stimulating agents and by screening a chemical compound library (>105 complexity) from NCI. Once validated, this technology will be transferred to the industry to facilitate their drug discovery effort. 3) To synthesize DC-stimulating peptoids. Peptoids (N-substituted glycine oligomers) have advantages over peptides in protease resistance, higher stability, and higher diversity. Peptoid libraries (>107 complexity) synthesized in split/pool fashions will be screened in bead-immobilized forms. "Hit" compounds will be transformed into soluble dimeric forms and modified by molecular shuffling to obtain DC-stimulating "lead" peptoids. 4) To synthesize DC-stimulating illumination. Using a tunable illumination device, we will search the universe of light by testing the impact of >107 different illumination. We will also test the concept that DC activation is inducible by photochemical cross-linking of surface receptors. 5) To determine biological consequences of DC activation by different agents. Newly identified DC-stimulating agents will be examined for their in vitro impact on gene expression profiles, surface phenotype, cytokine and chemokine production, and T cell-stimulating capacity of DC and for in vivo impact on Langerhans cells. We will analyze experimenta data using computational biology tools to define algorithms that govern DC activation processes. Our study wil provide new insights into DC biology and may lead to the development of novel adjuvants and therapeutics.